US soldier on discharge endlessly liable (5)
I believe the answer is:
given
'liable' is the definition.
(thesaurus)
'us soldier on discharge endlessly' is the wordplay.
'us soldier' becomes 'GI' (informal term for a US soldier).
'on' says to put letters next to each other.
'discharge' becomes 'vent' (both can mean to expel or give out).
'endlessly' means to remove the last letter.
'vent' with its final letter taken away is 'ven'.
'gi'+'ven'='GIVEN'
(Other definitions for given that I've seen before include "Handed over; an 18 dn" , "assumed fact" , "Lent?" , "Donated" , "Specified, stated" .)